Apparatus for measuring ash content of food stuff by ultraviolet radiation

ABSTRACT

A method for measuring ash content of food stuff is carried out by 1) preparing, with respect to food stuff samples whose ash content values are known, a calibration curve by a non-linear analysis of absorbance values and the known ash content of each sample, the absorbance values being obtained by irradiating light having particular wavelengths containing at least an ultraviolet ray band wavelength, the particular wavelength being specific to organic ingredients well coupled to inorganic ingredients which result in the ash content, and 2) deriving, with respect to a sample whose ash content value is unknown, an ash content value of the sample from absorbance values obtained by irradiating, on the sample, light having the particular wavelengths containing at least the ultraviolet ray band wavelength and from the calibration curve prepared in advance by the non-linear analysis. An apparatus for carrying out the method includes a light source section, a photo detecting section, a storing section for storing the calibration curve, and a calculation section for calculating, with respect to a sample whose ash content value is unknown, the ash content value based on the absorbance values and the calibration curve stored in the storing section. It is possible to speed up the measuring operation and to improve the measuring precision.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a method and an apparatus for measuringash content of food stuff based on absorbance values obtained byirradiating light on samples and a calibration curve determined inadvance, and more particularly to a method and an apparatus formeasuring the ash content by utilizing a state in which an organicingredient such as flavonoid pigment, phytic acid, pectin is wellcoupled to inorganic ingredients which results in the ash content.

(2) Description of the Related Art

The ash content is defined as the residue after the removable of organicingredients and water from food stuff and is considered to correspond tothe total quantity of the inorganic ingredients of the food stuff.Conventionally, for analyzing the ash content, the food stuff is heatedto, for example, 550° C., and the sample is reduced to ashes to theextent that the organic ingredients and water are removed and carbon isnot present whereby the total quantity of the residue is regarded as theash contents. In carrying out the conventional method for measuring theash content, a considerable time is consumed for the removable of theorganic ingredients and water.

There has been a constant demand for an apparatus with which themeasuring of the ash content can be carried out in a short time. In anattempt to meet such a demand, there has been proposed an apparatus formeasuring the ash content in which the content value of ash, which is aspecific ingredient of a sample, is measured in a short time based onthe absorbance value which is obtained by irradiating solely the nearinfrared rays on the sample whose ash content value is unknown and onthe calibration curve which is predetermined from the absorbance valuesobtained by irradiating the near infrared rays on the sample whose ashcontent value is known and from the known ash content value. For themeasurement of ash content of, for example, food stuff, the ash contentmeasuring apparatus available today has been improved by the correlationwith the actual ash content nearly up to about ±0.03%, and such ameasuring apparatus is being utilized for the measurement of ash contentin a product such as wheat flour in which its quality is greatlyinfluenced by the ash content. The ash content is utilized also in otherfood stuff, and the food industry is attaching importance to the ashcontent of food stuff in general.

Conventionally, in the case of the wheat flour, it has been the practiceto obtain the calibration curve based on the correlation with respect tothe ash content in the near infrared ray region. Also, the practice wasthat no attention was paid to the state in which the ash contentconcentrates at epidermis (surface layer portion) of a wheat grain andthe calibration curve was obtained based directly on the ash content anda predetermined ingredient. Thus, the measuring precision was no higherthan ±0.03%.

In a country like Japan where the content impurity for a product such aswheat flour is severely regulated, there is a need to improve measuringapparatuses for a still higher measuring precision. In Japan, the wheatflour is classified into small groups of classes and end uses accordingto the ash content. For example, the wheat flour with the ash contentbeing below 0.34% is classified as a special class, that with the ashcontent being 0.34% to 0.44% as a first class, that with the ashcontents being 0.44% to 0.56% as a second class, and that with the ashcontent being above 0.56% as a third class.

Thus, if there occurs a difference in the actual ash content value andthe measured ash content value obtained by using a measuring apparatus,the ranking of the wheat flour may be changed, and this affects not onlythe price of the product but also greatly affects the credibility of thequality of the product. Therefore, if an ash content measuring apparatuswhose measuring precision is low is used in the flour milling step, itis not possible to effectively control the ranks of the wheat flour. Themeasuring precision desirable in the flour milling step is in the orderof ±0.01%. Under the existing state of art, the rank control stilllargely depends on the sharp senses of the operator gained through theexperience.

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to overcome the problemsexisting in the prior art and to provide a method and an apparatus formeasuring ash content of food stuff, specifically of wheat flour, whichcan be used both in a wheat flour production line and a wheat flouranalyzing laboratory and with which it is possible to speed up themeasuring operation and to improve the measuring precision.

According to one aspect of the invention, there is provided a method formeasuring ash content of food stuff, comprising the steps of:

preparing, with respect to a plurality of food stuff samples whose ashcontent values are known, a calibration curve by a non-linear analysisof absorbance values of each sample and the known ash content value ofeach sample, the absorbance values being obtained by irradiating lighthaving particular wavelengths containing at least an ultraviolet rayband wavelength, the particular wavelengths being specific to organicingredients coupled to inorganic ingredients which result in the ashcontent; and

deriving, with respect to a sample whose ash content value is unknown,an ash content value of the sample from absorbance values obtained byirradiating, on the sample, light having the particular wavelengthscontaining at least the ultraviolet ray band wavelength and from thecalibration curve prepared in advance by the non-linear analysis.

The organic ingredients coupled well with inorganic ingredients whichresult in the ash content in the sample are, in the case of a wheatgrain, organic ingredients which are distributed unevenly at a surfaceportion of the wheat grain as is the case with the ash content in thewheat grain which is distributed largely at a surface portion of thewheat grain. These organic ingredients include flavonoid pigment, phyticacid and pectin.

In the method for measuring ash content of food stuff, the light havingthe particular wavelengths may range from ultraviolet rays to visiblerays.

Also, the light having the particular wavelengths may range fromultraviolet rays to near infrared rays.

Further, the light having the particular wavelengths may compriseultraviolet rays and near infrared rays.

In the method for measuring ash content of food stuff, the absorbancevalue derived from any of said near infrared rays may be used to correctinfluence, such as by water, temperature and grain sizes, to themeasuring precision.

Also, in the method, the step of preparing the calibration curve by thenon-linear analysis may be carried out using neural networks.

According to another aspect of the invention, there is also provided anapparatus for measuring ash content of food stuff comprising:

a light source section for irradiating, on a sample, light havingwavelength containing at least an ultraviolet ray band wavelength whichis capable of detecting organic ingredients coupled to inorganicingredients which result in the ash content;

a photo detecting section for detecting at least one of reflected lightand transmitted light from the sample;

a storing section for storing in advance a calibration curve prepared,with respect to a plurality of food stuff samples whose ash contentvalues are known, by a non-linear analysis using neural networks basedon absorbance values of each sample and on the known ash content valueof each sample, the absorbance values being obtained by irradiatinglight having particular wavelengths containing at least an ultravioletray band wavelength;

a calculation section for calculating, with respect to a sample whoseash content value is unknown, absorbance values from at least one of thereflected light and the transmitted light obtained from the photodetecting section by irradiating light having the particular wavelengthscontaining at least the ultraviolet ray band wavelength, and forcalculating, with respect to the sample whose ash content value isunknown, an ash content value based on the absorbance values and thecalibration curve stored in the storing section; and

a control section for controlling the light source section, a photodetecting section, a storing section and an operation section.

In carrying out the present invention, the state in which the ashcontent is concentrated at epidermis of a wheat grain was taken intoconsideration and, by selecting the organic ingredients well coupled toinorganic ingredients which result in ash content, it was made possibleto confirm that the ultraviolet rays are most suited to the detection ofthe inorganic ingredients. Thus, the invention enables the improvementof the measuring precision significantly up to ±0.01%. The ingredientssuch as flavonoid pigment, phytic acid, pectin demonstrate significantchanges in minute intervals in the ranges from the ultraviolet rayregion to the visible ray region as compared with those in the nearinfrared ray region so that, by using the ultraviolet ray region, it hasbecome possible to detect minute changes in the absorbance values.

On the other hand, the attention was paid to the state that, in the nearinfrared ray region, the absorbance values tend to be shifted by theinfluence of water, temperature and grain sizes, it has been arranged toeffect the correction of the influence of the water, temperature andgrain sizes in the ultraviolet ray region and the visual ray region and,with this arrangement, the measuring precision can be further enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be apparent from the following description of preferredembodiments of the invention explained with reference to theaccompanying drawings, in which:

FIG. 1 is a graph showing absorbance characteristic curve obtained byirradiating on the wheat flour the light having the wavelength bandsranging from the ultraviolet rays to the near infrared rays;

FIG. 2 is a flow diagram showing a process flow in the flour millingsystem used in the embodiment; according to the invention;

FIG. 3 is a diagram for use in explaining the measuring principle of theash content (inorganic ingredients) measuring apparatus according to theinvention;

FIG. 4 is a diagram for showing the construction of the particleingredient measuring unit of the apparatus;

FIG. 5 is a diagram for showing the sample supplying path and the bypassprovided in the measuring cell;

FIG. 6 is a front view, partially broken away, of the measuring cell;

FIG. 7 is a top view, partially broken away, of the measuring cell;

FIG. 8 is a side view showing main elements of the measuring cell;

FIG. 9 is a block diagram for showing the measuring unit and theingredient calculation control unit; and

FIG. 10 is a schematic representation of neural networks.

PREFERRED EMBODIMENT OF THE INVENTION

Now, a preferred embodiment of the invention is explained with referenceto an example in which ash content of food stuff, especially of wheatflour is measured.

With respect to a sample whose ash content value is known, confirmationis made for organic ingredients well coupled to inorganic ingredientswhich result in the ash content in a sample grain, i.e., in a grain nothaving been processed. For example, flavonoid pigment is highlycorrelative with the ash content and, when this pigment is measured, themeasured value serves as an important material or factor for therecognition of the color of the wheat flour which is representative ofthe mixing rate of bran, and from this it is apparent that the flavonoidpigment is in a proportional relationship with respect to the ashcontent. Further, the inorganic ingredients contained in the wheat flourmay include calcium, iron, phosphorus, potassium, sodium, magnesium,iodine, etc. Among these ingredients, the largest content ingredient isphosphorus (P) which occupies 50% of the total content. With respect tophosphorus, it is considered that the probability is high for thephosphorus to be present in the state in which it is well coupled tophytic acid which is an organic ingredient in a wheat grain. In the caseof the wheat grain, the ash content is largely present in a surfaceportion of the wheat grain.

As explained above, the organic ingredients well coupled to theinorganic ingredients which result in the ash content include flavonoidpigment, phytic acid, pectin and protein. The inorganic ingredientswhich result in the ash content are, among the overall inorganicingredients, the inorganic ingredients which are well coupled to theorganic ingredients such as flavonoid pigment, phytic acid and pectin,and these organic ingredients are highly correlative with respect to theash content. According to the present invention, attention is given tothese organic ingredients, and particular wavelengths with which theabsorbance changes proportionally to the ash content of these organicingredients are determined. For these particular wavelengths, variouswavelength bands can be used and, although they cannot be uniformlydecided for different organic ingredients, the light irradiated is ofthe wavelength bands of ultraviolet rays, visual rays and near infraredrays, and the wavelength bands of the ultraviolet rays or the wavelengthbands ranging from the ultraviolet rays to the visual rays are the mainwavelength bands.

FIG. 1 shows absorbance characteristics obtained by irradiating on thewheat flour the light having the wavelength bands ranging from theultraviolet rays to the near infrared rays. When the irradiation is madeon the above-mentioned organic ingredients, the wavelength which hasdemonstrated specially remarkable changes is the ultraviolet ray region,and this is the wavelength band in which differences in the absorbancevalues can easily be confirmed. The absorbance values in this wavelengthband play an important role in the preparation of the calibration curvewhich is later used for the calculation of the ash content.

After determining the particular wavelengths in the ultraviolet rayregion or the visual ray region and the near infrared ray region, thelight of the particular wavelengths of each wavelength band isirradiated on a sample whose ash content value is already known. Basedon the absorbance value obtained from the irradiated sample and the ashcontent of the known sample, a calibration curve is prepared bynon-linear analysis using neural networks. Here, the networksconstructed for the calculation of the ash content are constituted bythree layers, namely, an input layer, a hidden or a hidden layer and anoutput layer as shown in FIG. 10. Inputted to each of nine units of theinput layer is each of absorbance values x₁, x₂, . . . , x₉ obtainedrespectively from nine particular wavelengths irradiated on the wheatflour, and the data is processed at 45 units of the hidden layer. Fromthe hidden layer, there are outputted t₁, t₂, . . . , t₄₅, and they areinputted into one output layer unit and finally the ash content value yof the wheat flour is outputted. More specifically, the weight w_(ka)obtained by the correction (teeting) of the networks is set between thek-th input layer unit (k=one of 11 to 9) and a-th hidden layer unit(a=one of 1 to 45), and the absorbance value x_(k) inputted to the inputlayer is inputted to the a-th hidden layer as a value w_(ka) ·x_(k)obtained by the multiplication with the set weight w_(ka). At the a-thhidden unit, the sum total Sa of w_(ka) ·x_(k) inputted from each inputlayer unit as in Equation 1 is calculated. ##EQU1## wherein θ_(a) is abias of the a-th hidden layer unit, and is a value obtained in advancethrough the teeting.

Next, as in Equation 2, the sigmoid conversion is carried out for Sa.##EQU2## wherein T represents a network temperature and a gain(constant). The weight V_(a) obtained through the teeting is set betweenthe output layer unit and the a-th hidden layer unit, and the output tacalculated at the hidden layer is outputted to the output layer as thevalue v_(a) ·t_(a) multiplied with the set weight v_(a).

At the output layer unit, as in Equation 3, the sum total u of v_(a)·t_(a) inputted from each hidden layer unit..pa ##EQU3## wherein η is abypass of the output layer unit, and is a value obtained in advance bythe teeting.

Finally, as in Equation 4, the sigmoid conversion is carried out for u,and the y which is the ash content value is outputted. ##EQU4##

For architecting the networks, the absorbance values and the ash contentvalues of wheat flour of a plurality of kinds of wheat flour whose ashcontent values are known, for example, several hundred kinds of wheatflour, are used. The networks are provided with a plurality of patternseach representing such a rule as "where the absorbance value x is acertain value, the ash content value is y", and the networks are revisedby "learning". The calibration curve prepared by the non-linear analysisusing the neural networks as above is incorporated as an analytical soft(ROM) into the ash content measuring apparatus.

By using the above calibration curve, the ash content of an unknownsample can be worked out based on this calibration curve and theabsorbance values obtained by irradiating, on the sample whose ashcontent value is unknown, the light having the above-mentionedparticular wavelengths.

In the foregoing, the explanation has been made for the case where thelight of the nine kind particular wavelengths is irradiated, but thewavelength may well be only ultraviolet region wavelengths or may rangefrom an ultraviolet ray region to a visible ray region. Further, wherethe near infrared ray region is used as a wavelength band for making anappropriate correction during the preparation of the calibration curve,the measurement precision can be enhanced. Although it is explained thatthe light of the nine kind particular wavelengths is irradiated, thesewavelengths are not limited to the nine kinds.

The inventors have conducted various tests by irradiating the light ofvarious wavelengths, and some of the test results are hereinafterexplained. Table 1 shows the correlation coefficient and the measurementprecision in the case where the absorbance values are obtained byirradiating the light of particular wavelengths ranging from anultraviolet ray region to a visible ray region and the ash content valueis calculated based on the absorbance values thus obtained.

                  TABLE 1    ______________________________________    Ash content level 0.4-0.5 0.6-0.8    Correlation coefficient                      0.919   0.963    Measuring precision                      0.013   0.018    Wavelength (nm)    221               *       *    354               --      *    408               *       *    425               *       *    442               *       --    ______________________________________     *Wavelength used

Further, Table 2 shows the correlation coefficient and the measurementprecision in the case where, while the absorbance values obtained byirradiating the light of particular wavelengths ranging from theultraviolet ray region to the visible ray region are the main values,the absorbance values obtained by irradiating the light of particularwavelengths in the near infrared ray region are added thereto for thepurposes of corrections.

                  TABLE 2    ______________________________________    Ash content level 0.4-0.5 0.6-0.8    Correlation coefficient                      0.942   0.983    Measuring precision                      0.010   0.012    Wavelength (nm)     221              *       *     354              --      *     408              *       *     425              *       *     442              *       --    1915              --      *    2178              --      *    2300              *       --    ______________________________________     *Wavelength used

As above, the invention makes it possible to greatly enhance themeasurement precision as compared with that in the conventional methodwherein the wavelengths of only the near infrared ray region are used,the enhanced measurement precision being about 0.01%. Table 2 shows thatthe measurement precision can be further enhanced when the near infraredray region is additionally used. The use of the near infrared ray regionenables the correction of the influence to the measurement precisionthat may be caused by changes in water content, temperature, particlesizes, etc.

FIG. 2 shows an example of a flour milling system which the presentinvention employs and which is generally used for milling grains such aswheat grains. The system has as its main elements four milling machines1, 2, 3, 4 and three sifters 5, 6, 7. Through a pneumatic transportingmeans, the first milling machine 1 is communicated to a cyclone 8 whichis provided, at its lower portion, with an air lock valve 9 and aswitching valve 10, is communicated to a measuring section 11 such that,with the action of the switching valve 10, the ground particles arepartially supplied to the measuring section 11 where the measurement ofthe ash content of such particles is carried out, and is communicated toan inlet of the first sifter 5. The sifter 5 can make the sorting inthree stages depending on particle sizes, and has a large particle sizeoutlet 12, a medium particle size outlet 13, and a small particle sizeoutlet 14. The large particle size outlet 12 is communicated to an inletof the first milling machine 1, the medium particle size outlet 13 iscommunicated to an inlet of the second milling machine 2, and the smallparticle size outlet 14 is communicated to a cyclone 15.

Also, through a pneumatic transporting system, the second millingmachine 2 is communicated to the cyclone 15 which is provided, at itslower portion, with an air lock valve 16 and a switching valve 17, iscommunicated to a measuring section 18 such that, with the action of theswitching valve 17, the ground particles are partially supplied to themeasuring section 18 where the measurement of the ash content of suchparticles is carried out, and is communicated to an inlet of the secondsifter 6. The sifter 6 can make the sorting in three stages depending onparticle sizes, and has a large particle size outlet 19, a mediumparticle size outlet 20 and a small particle size outlet 21. The largeparticle size outlet 19 is communicated to an inlet of the secondmilling machine 2, the medium particle size outlet 20 is communicated toan inlet of the third milling machine 3, and the small particle sizeoutlet 21 is communicated to a cyclone 22.

Next, through a pneumatic transporting system, the third milling machine3 is communicated to the cyclone 23 which is provided, at its lowerportion, with an air lock valve 24 and a switching valve 25, iscommunicated to a measuring section 26 such that, with the action of theswitching valve 25, the ground particles are partially supplied to themeasuring section 26 where the measurement of the ash content of suchparticles is carried out, and is communicated to an inlet of the thirdsifter 7. The sifter 7 can make the sorting in three stages depending onparticle sizes, and has a large particle size outlet 27, a mediumparticle size outlet 28 and a small particle size outlet 29. The largeparticle size outlet 27 is communicated to an inlet of the fourthmilling machine 4, the medium particle size outlet 28 is communicated toa cyclone 30, and the small particle size outlet 29 is communicated to acyclone 31. The fourth milling machine 4 is communicated, throughpneumatic transporting means, to a cyclone 23.

The exhaust of the cyclones 8, 15, 23 is communicated to a cyclone 33through a blower 32, the exhaust of the cyclones 22, 31, 30 iscommunicated to a cyclone 35 through a blower 34, and the exhaust of thecyclones 33, 35 is discharged to the outside through a bag filter 36.The cyclones 22, 30, 31, 33, 35 are respectively provided, at theirlower parts, with air lock valves 37, 38, 39, 40, 41, and arecommunicated to inlets of particle receiving tanks 42, 43, 44 forstoring the ground materials. The system explained above is a generallyused flour milling system for grains such as wheat grains.

The ash content measuring apparatus according to the invention isexplained in detail with reference to FIGS. 3 and 9.

The light source 81 with which it is possible to irradiate the lighthaving particular wavelengths capable of detecting the organicingredients well coupled to inorganic ingredients which result in theash content is preferably one with which it is possible to irradiate thelight ranging from the ultraviolet ray region to the near infrared rayregion. In the embodiment, it is arranged that, by using a tungsteniodine lamp 82 and a deuterium lamp 83, the light having the wavelengthsin a range of 190 nm to 2500 nm can be irradiated. More specifically,the tungsten iodine lamp 82 can irradiate the light having thewavelengths in a range of 190 nm to 350 so that it is used for theultraviolet ray region, and the deuterium lamp 83 can irradiate thelight having the wavelengths in a range of 330 nm to 2500 nm so that itis used for the visual ray region and the near infrared ray region. Forthe ultraviolet ray region, two lamps are used and, by switching, thelight in the ultraviolet ray region in a range of 300 nm to 380 nm canbe irradiated. That is, by changing angles of the reflecting mirror 84,the switching between the two lamps can be effected. The light switchedat the reflecting mirror 84 passes through a filter 85 and a slit 86,and is made the light of a unit wavelength by a diffraction grating 87.This diffraction grating 87 is constituted by gratings which aredifferent from each other at its front and back, so that the switchingmay be made between the front and the back depending on desiredwavelengths.

The photo detecting section 88, which detects the light transmitted (orreflected) from the organic ingredients when the sample is irradiated bythe light from the light source 81, may receive the transmitted lightdirectly by a light receiving element, or may be arranged such that thetransmitted light is lead to an integration sphere whereby the lightintensity is calculated. The light receiving element is equipped with avisual ray/ultraviolet ray receiving element 89 and a near infrared rayreceiving element 90 and, while the switching is made by a mirror 93between the light 92 transmitted through the sample and the referencelight 91, the light received is measured at each light receivingelement.

In the embodiment of the invention, the light receiving element isincluded in an optical processing unit 59 (FIG. 7). Signals from theoptical processing unit 59 having the light receiving element areconverted to absorbance values by a sample measuring control unit 57(FIG. 9).

The calibration curve is prepared by a non-linear analysis using neuralnetworks based on the absorbance values of the organic ingredientsobtained by irradiating, on the sample whose ash content value is known,the light having the above-mentioned particular wavelengths and on theash content of the known sample, and this calibration curve is stored ina storing section 76 of an ingredient calculation control unit 52 (FIG.9).

Also, the ingredient calculation control unit 52 includes a calculationsection 77 which calculates the absorbance values based on the intensityof the reflected or transmitted light obtained by the photo detectionsection 88 for the unknown sample, and calculates the ash content valueof the unknown sample based on the absorbance value and the calibrationcurve stored in the storing section 76.

Further, the ingredient calculation control unit 52 includes a controlsection 78 which interconnects and controls various sections. Forscaling down the apparatus, the sample measuring control unit 57 and theingredient calculation control section 52 may be combined into anintegral unit.

The embodiment of the invention is explained further in detail withreference to FIGS. 4 to 8. FIG. 4 shows an overall arrangement whichrelates to the particle ingredient measuring unit 50. The particleingredient measuring unit 50 is constituted by a measuring unit 51 andthe ingredient calculation control section 52 which receives signalsfrom the measuring unit 51, which calculates the ash content value andwhich is connected to an external unit 53 which performs variousprocessings according to the calculated ash content value. To themeasuring unit 51 is connected a suction means 56 constituted by asuction fan 54, a cyclone 55, etc.

The measuring unit 51 includes, in addition to the sample measuringcontrol unit 57, a measuring cell 58 and the optical processing unit 59.A particle sample is supplied from above the measuring cell 58 and,after the measuring process, is discharged downwardly from the measuringcell 58. The detail of the process is explained starting from themeasuring cell 58. As shown in FIG. 5, the measuring cell 58 isprovided, at its upstream, with a sample supplying path 61 for supplyingthe particle sample to the measuring cell 58 from a transporting path 60of the flour milling system, and the sample supplying path 61 at theupstream is connected to the transporting path 60 through anopening/closing means 62 controlled by the sample measuring control unit57. Also, the measuring cell 58 is provided with a sample bypass 73(explained later).

Now, the measuring cell 58 is explained with reference to FIGS. 6 to 8.The measuring cell 58 is constituted by a cylinder 63 of an optionallength disposed in a vertical direction, and is provided, at its lowerportion, with a valve means 66 consisting of a valve 64 for enabling thebatch processing of particles and a driving means 65 for causing thevalve 64 to be opened or closed. A cylinder wall disposed above thevalve means 66 has a measuring window 67 for permitting the measurementof the light reflected from the particles within the cylinder of themeasuring cell 58. Further, the measuring cell 58 includes a pressingmeans 70 consisting of a pressing member 68 which moves backward orforward with respect to the measuring window 67 and which presses theparticles within the cylinder of the measuring cell 58 and a drivingmeans 69 which drives the pressing member 68 for backward or forwardmovement. Also, at a position above the measuring window 67, there isprovided a jetting means 72 having a plurality of air jetting holes 71which communicate to an air compressing means (not shown) such as acompressor and which clean the particles inside the measuring cell 58.The air jetting holes 71 of the jetting means 72 are arranged such thatthe air is directed at least to the measuring window 67 and the pressingmember 68 of the pressing means 70. The optical processing unit 59 facesto the measuring window 67 so that the light is irradiated on theparticles, the reflected light is received, and the signals received areinputted to the sample measuring control unit 57 (FIG. 4). It ispreferred that the measuring window 67 be formed by a plate materialsuch as an anhydrous quartz glass which does not affect the opticalspectrum analysis and that the shape of the measuring window 67 be of aflat surface so as to allow the incident light or the reflecting lightto pass through vertically thereof. However, it is not precluded to formthe measuring window 67 in a curved surface along the inner peripheralshape of the measuring cell.

The measuring cell 58 is provided with the sample bypass 73. The samplebypass 73 has its one portion connected to a lower portion of the valvemeans 66 and another portion connected to the suction means 56, has themeasuring cell 58 provided in parallel with the cylinder 63, and has acommunication path 74 provided above the measuring window 67 of themeasuring cell so as to communicate with the measuring cell 58. Thesuction means 56 is connected to the sample bypass 73 and the suckingforce acts upwardly of the bypass 74 so that the overflow sampleparticles from the measuring cell 58 are sucked into the bypass 73through the communication path 74 and naturally fall by gravitydownwardly of the bypass 73. If the sucking force of the suction means56 is too strong, the sample particles present in the bypass 73 are allsucked towards the suction means 56, so that the balancing thereof withrespect to the sucking force of the transporting path 60 is necessary.

In the vicinity of the measuring window 67, there is provided a particledetection sensor 75. Only when the particle detecting sensor 75continues to output a detection signal for, for example, 5 seconds, theopening/closing means 62 is closed and the pressing means 70 is causedto act. The pressing means 70 is operated so as to press the sampleparticles within the cylinder 63 of the measuring cell and, in this way,it can be ensured that the sample particles are properly supplied to andheld at the measuring cell.

FIG. 9 shows, in a block diagram, the controlling operation of theparticle ingredient measuring unit. The pressing means 70, the valvemeans 66, the air jetting means 72 and the opening/closing means 62 ofthe measuring cell 58 are all connected to and controlled by the samplemeasuring control unit 57. The particle detection signal from theparticle detecting sensor 75 and the measuring signal from the opticalprocessing unit 59 are inputted into the sample measuring control unit57. The sample measuring control unit 57 converts the received signalsinto absorbance values which are inputted into the ingredientcalculation control unit 52 as outputs of the measuring unit 51. Theabsorbance values outputted may be non-continuous absorbance values inparticular wavelengths or may be continuous absorbance value componentsobtained by scanning at minute intervals and, depending on the contentsof particle ingredients sought for the intended purposes or on thegeneralized use, the unit is constructed such that it is economical andis capable of carrying out, the measuring operation in efficient ways.At the particle ingredient measuring unit 52, the absorbance valuesoutputted from the measuring unit 51 are received and the ash contentvalue is calculated. The particle ingredient measuring unit 52 includesthe storing section 76 which stores in advance the calibration curve tocalculate the ash content value from the absorbance values, thecalculation section 77 which calculates the ash content value from theabsorbance values obtained based on the calibration curve, and thecontrol section 78 which interconnects and controls these sections.

Next, the overall measuring sequences are explained with reference to ablock diagram of FIG. 9. At the starting of the process operation of theflour milling system (external system) 53, a measurement starting signalis inputted from the flour milling system into the ingredientcalculation control unit 52. With this signal, a starting signal isinputted from the ingredient calculation control unit 52 into the samplemeasuring control unit 57 of the measuring unit 51. When the startingsignal is inputted into the sample measuring control unit 57, the samplemeasuring control unit 57 outputs a signal for the valve means 66 to beclosed and the opening/closing means 62 to be opened. The sampleparticles are supplied to the measuring cell 58 from the transportingpath 60 of the particles through the opening/closing means 62 and thesample supplying path 61. When the sample particles fully fill themeasuring cell 58, the excess sample particles flow to the sample bypass73 through the communication path 74 and return to the transporting path60 through the sample supplying path 61. At this time, the particledetecting sensor 75 in the measuring cell has already detected the statethat the sample particles are filled. That is, the sample measuringcontrol unit 57 is so arranged as to judge that the measuring cell 58 isfull when the detection signal of the particle detection sensor 75continues for a predetermined period of time. In this embodiment, if thedetection signal by the particle detecting sensor 75 continues for 5seconds, it is judged that the sample particles in the measuring cell 58have reached the amount that is appropriate for the measurement.

With this continued detection signal by the particle detecting sensor75, the sample measuring control unit 57 controls the opening/closingmeans 62 to be closed so that no further sample particles are taken-inand also controls the pressing means 70 so that its pressing member 68is driven towards and against the measuring window 67. When the drivingof the pressing means 70 is completed, the sample measuring control unit57 of the measuring unit 51 outputs to the ingredient calculationcontrol unit 52 a signal indicating that the preparation for measuringthe absorbance values of the sample particles has been completed. Theingredient calculation control unit 52 outputs to the sample measuringcontrol unit 57 a signal for requesting the absorbance values. Uponreceipt of the request for the absorbance values, the optical processingunit 59 which faces to the measuring window 67 of the measuring cell 58irradiates on the particles the predetermined light such as ultravioletrays, visual rays and near infrared rays for enabling the detection ofreflecting light or transmitted light from the particles. Thewavelengths of the light irradiated may vary such as continuouswavelengths, limited wavelengths of a plurality of kinds, andwavelengths with predetermined intervals, and needless to say that thewavelengths of the irradiated light are different depending on theingredients to be analyzed. The selection of these wavelengths is basedon the ingredient spectrum analysis available heretofore.

The reflected light received is sent from the optical processing unit 59to the sample measuring control unit 57 where the light is converted tothe absorbance values. The absorbance values converted are sent, onrequest, to the ingredient calculation control unit 52. When themeasurement of the absorbance values is completed, the sample measuringcontrol unit 57 outputs to the ingredient calculation control unit 52 asignal indicating that the absorbance value measuring has beencompleted.

Where the temperature correction is carried out, although this has notbeen explained in detail with respect to the embodiment described above,it is possible to add a step wherein, by providing a temperaturedetection element in the measuring cell 58, the ingredient calculationcontrol unit 52 outputs to the sample measuring control unit 57 atemperature requesting signal, and the sample measuring control unit 57takes-in a signal from the temperature detecting sensor 79 andimmediately outputs this signal to the ingredient calculation controlunit 52. In this way, it is made possible to correct the temperature byusing the spectrum analysis method which is susceptible to be influencedby the temperature. The storing section stores in advance thecalibration curve prepared based on the absorbance values obtained bymeasuring the samples whose ash content values are known and on the ashcontent values of the samples and, at the ingredient calculation controlunit 52, the calculation curve is used, the absorbance values whose ashcontent value is unknown are measured, and the ash content of the sampleis calculated. Here, the explanation has been made on the measurement ofthe ash content only but, in the case where the wheat flour is thesubject of the measurement, this is not limited thereto as it is alsopossible to measure protein, water content, damaged starch, waterabsorption, color, etc. similarly as in the prior art.

When the outputting of data from the sample measuring control unit 57has all been completed, the pressing by the pressing means 70 isimmediately released so that the valve 64 of the valve means 66 isopened and the sample particles in the measuring cell 58 are discharged.Thereafter, the jetting means 72 is driven to clean the measuring window67, the pressing member 68 and the inside of the measuring cell 58. Thejetting means 72 is realized by a magnetic valve which functions as anair valve having a jet hole, and is connected to the air compressingmeans such as a compressor not shown. The air shower within themeasuring cell 58 continues for a predetermined period of time and, atthe point when the sample measuring control unit 57 has confirmedthrough the particle detecting sensor 75 that the sample particles arenot present, the ingredient calculation control unit 52 turns to astand-by state for the starting signal and, when the starting signal isinputted, the opening/closing means 62 is opened. By repeating thisoperation, the measurement of ash content for sample particles iscarried out.

In the foregoing, the measuring cell has been explained as being acylindrical body. However, what is required is that the body is hollowso that the section of the body may well be round or square.

While the invention has been described in its preferred embodiment, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeof the invention as defined by the claims.

What is claimed is:
 1. An apparatus for measuring ash content of a foodstuff sample comprising:a light source section for irradiating, on asample, light having a wavelength containing at least an ultraviolet rayband wavelength, said ultraviolet ray band wavelength detects the ashcontent of a food stuff sample; a photo detecting section, communicatingwith said light source section, for detecting an intensity of reflectedlight or transmitted light from said sample by irradiating said samplewith said ultraviolet ray band wavelength from said light sourcesection; a storing section for storing in advance a calibration curveprepared, with respect to a plurality of food stuff samples whose ashcontent values are known, by a non-linear analysis using neutralnetworks based on absorbance values of each of said plurality of foodstuff samples and on the known ash content value of each of saidplurality of foodstuff samples, said absorbance values being obtained byirradiating each of said plurality of food stuff samples with lightcontaining said ultraviolet ray band wavelength from said light sourcesection; and a calculation section, communicating with said storingsection, for calculating, with respect to a sample whose ash contentvalue is unknown, absorbance values from the intensity of said reflectedlight and said transmitted light obtained from said photo detectingsection, and for calculating, with respect to the sample whose ashcontent is unknown, an ash content value based on said absorbance valuesof said sample whose ash content value is unknown and said calibrationcurve stored in said storing section.